The present invention relates to bridging or sealing gaps in building structures. These gaps or joints are typically provided to permit expansion and contractions of building components such as walls, floors, ceilings and roofs. In particular, the present invention relates to a hollow, elongated, elastic joint seal or filler which is compressed when located in such gaps with the hollow portions of the seal being defined by an arrangement of interior wall/dividers which interact to change the structural characteristics of the seal after compression.